The mammalian strategy of internal gestation followed by lactation imposes severe constraints on what males can do in terms of parental investment. This asymmetry in the processes of reproduction results in male mammals placing disproportionate emphasis on mating strategies and less on parental care than is typical of most other taxa. Although male mammals can contribute indirectly to parental care (e.g. by defending a feeding territory for the females(s) or acting as an anti-predator defence), this only remains an option where females can gain a net benefit from associating with males relative to the foraging costs that additional animals must inevitably impose on them.

This asymmetry in reproductive biology has one important implication for mammalian social systems. In birds, it is not uncommon for males to arrive first on the breeding ground.Having partitioned the available space among themselves, they settle on their territories to await the arrival of the females who then choose among them. While a similar pattern can be observed in those mammals that adopt a lek mating system (notably some deer, antelope and pinnipeds), the reverse is probably more typical of many mammals (and most primates). In a classic experiment, Charles- Dominique (1977) released a number of dwarf galago (Galago demidorvii) into a forest in Gabon. He found that the population developed its own natural structure in a surprisingly ordered manner. First, the females established their ranges; once they had decided how to distribute themselves, the males then mapped themselves onto the female distribution.